Magnetic reed switch with latching feature



Jan. 19, 1965 E. w. WERTS 3,166,652

MAGNETIC REED SWITCH WITH LATCHING FEATURE Filed April 17, 1965 INVENTOR. EVERETT W. WERTS,

19y '7 we ATTORNEY.

United States Patent 3,166,652 I MAGNETHI REED SWITCH WITH LATCHING FEATURE Everett W. Werts, Normal, 111., assignor to Qeneral "lectric Company, a corporation of New York Filed Apr. 1'7, 1963, Ser. No. 273,772 6 Claims. Cl. 2tltl87) This invention relates to magnetic reed switches and has particular relation to sealed latch-type reed switches with a Permanent Memory characteristic.

Latch-type reed switches with a Permanent Memory characteristic have heretofore included a sealed tube containing a defiectable reed having a contact portion located between and overlapping a pair of fixed contacts in the form of a pair of oppositely poled permanent magnets. The arrangement is such that when the reed has been deflected to either of the fixed contacts by application of an external magnetic field, the reed will remain in engagement with such fixed contact after removal of the external field. The reed is switched to the other fixed contact by application of an external field having a polarity opposite to that of the previously applied external field.

In latch type switches of this general nature it is desirable that the switch include a minimum number of inexpensive parts arranged in a manner so that the switch has minimum dimensions and is of low cost construction. Also, such switches desirably should exhibit good operating sensitivity so that a very small external magnetic field is capable of deflecting the reed to operate the switch. Further, it is very desirable that the switch design be such that adequate holding forces are provided to retain the reed in engagement with the fixed contact to which it has been deflected after removal of the external field. Further, substantial contact opening forces should be provided for assuring opening of the contacts in the event of contact sticking or welding. It isalso advantageous that the switch design be such that the permanent magnets can be magnetized and their inductions set to provide desirable switch operating characteristics after the switch is assembled. Previous designs of reed switches with a Permanent Memory characteristic have not'been entirely satisfactory in that they have failed to incorporate one or more of the above desirable features.

It is therefore a primary object of the present invention to provide a novel and improved sealed magnetic reed switch with a Permanent Memory characteristic.

It is another object of the invention to provide a novel and improved Permanent Memory sealed magnetic reed switch having excellent operating sensitivity so that the reed switch including a pair of permanent magnets arranged so that their magnetic influence can be readily varied after the switch is assembled.

, In carrying out the invention in one form a doublethrow Permanent Memory magnetic reed switch is provided including a sealed tube which mounts at one end a pair of spaced fixed electrodes of electrically and magnetically conductive material having terminal parts outside the tube and contact parts inside the tube in spaced relation. The tube also mounts at its other end an elec- 3,166,652 Patented Jan. 19, 1965 trically and magnetically conductive deflectable reed having a terminal part outside the tube and a contact part inside the tube extending between the fixed contact parts in overlapping relation therewith. A first permanent magnet is located on one of the electrodes for attracting the reed toward such one electrode, and is positioned with its poles spaced longitudinally of the tube so that magnetic flux therefrom passes through. a portion of its associated electrode and lengthwise through a substantial portion of the reed. A second permanent magnet is positioned outside the tube on the external surface thereof with its poles also spaced longitudinally of the tube so that magnetic flux therefrom passes through a portion of the other electrode and lengthwise through a substantial portion of the reed. The two permanent magnets are poled in the same direction so that magnetic fluxes therefrom pass through the reed in opposite directions. The switch is adapted for association with external magnetic field producing means arranged to produce magnetic flux effective to transfer the reed between the two fixed electrodes, the permanent magnets being effective to retain the reed in either of its deflected positions after removal of the external field.

. Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FlG. 1 is a view in elevation with parts broken away and with parts shown in section of a sealed Permanent Memory magnetic reed switch constructed in accordance with the present invention, and

FIG. 2 is a view with parts broken away and with parts shown in section of a switch of different construction than the switch of FIG. 1.

Referring now to the drawings there is illustrated in FIG. 1 a Permanent Memory double-throw reed switch S constructed according to the present invention and preferably incorporating the basic double-throw switch arrangement described and claimed in application S.N. 190,274 filed April 26, 1962 by Everett W. Werts now Patent No. 3,117,202 andassigned to the assignee of the present invention. The double-throw reed switch shown in FIG. 1 includes an elongated glass tube 10 sealed at its opposite ends and mounting at one end a pair of fixed electrodes 11 and 12 formed of electrically and magnetically conductive material, such as a nickel-iron alloy, the electrodes including respectively longitudinally extending spaced terminal parts 13 and 14 having portions both inside and outside the tube and contact parts 15 and 16 located within the tube in transverse spaced relation. electrically and magnetically conductive reed 17 is supported by the tube and includes a terminal portion 13 extending outside thereof and a longitudinally extending deflect able contact part 19 Within the tube andextending between the contact parts 15 and 16 inoverlapping relation therewith. The reed 17 is defiectable into .and out of engagement with the contact parts 15 and 16 and when the reed 17 is deflected to engage either of the contact parts, the reed develops a spring force which urges it away from the engaged contact part .to provide a very effective contact-separating force. Electrical connections are made to the terminal parts 13, 14 and 18.

A first permanent magnet 20 is included in a first magnetic circuit which includes the electrode 12 and the reed 17. The magnet 20 is mounted on the electrode 12 and in the embodiment shown in FIG. 1 is located inside the tube 10 for attracting the reed 17 toward the contact part 16. The magnet 20 may be formed of any suitable permanent magnetic material, such as Alnico, and is positioned so that its North and South poles are spaced longitudinally of the tube and the magnet itself is space longitudinally of the contact part 16. For this purpose Anv the magnet 20 is mounted by terminal part 14 of the electrode 12 which is of two-part construction, and the contact part 16 of the electrode 12 is mounted by the magnet 219. The contact parts 15 and 1d are of generally conforming stepped configuration and the right hand ends thereof as viewed in FIG. 1 are located substantially equal distances from the inner wall of the tube 10. If desired, the magnet 21? may be mounted on the terminal part 14 externally of the tube 11) as will presently appear. Magnetic flux emanating from the magnet 25 is designated .by the dash lines A, and it is seen that this magnetic traverses portions of the electrode 12 and also traverses a substantial longitudinal section of the reed 17. The magnetic flux A is effective to attract the contact part 19 of the reed towards the contact part 15 of the electrode 12, and by varying the induction of magnet 26 the degree of attraction of reed 17 to the contact part 15 may be varied.

In accordance with the present invention an additional magnet'22 formed of a material such as Alnico is positioned and arranged to attract the contact part 19 or" reed 17 toward the contact part 15 of the electrode 11. The magnet 22 is locatedoutside the tube and is secured to the external surface thereof as by cementing with its magnetic poles spaced longitudinally of the tube. The magnets 20 and 22 are poled in the same direction so that magnetic fluxes emanating from the magnets 21) and 22 traverse the reed 17 lengthwise in opposing directions. It is noted that flux designated by dash lines B emanating from the magnet 22 traverses a portion of the electrode 11 and a substantial longitudinal portion of the reed 17. In FIG. 1 the reed 17 is shown deflected into engagement with the contact part 16 of electrode 12.

In order to control operation of the switch, magnetic field producing means is provided illustrated in the form of a winding 23 having a number of turns surrounding the tube 10. While the field producing means is shown in the form of a winding, it can be appreciated that the field producing means may assume other forms such as a permanent magnet. Magnetic flux produced in response to energization of the winding 23 by current fiow- "ing in the winding in the direction of the arrow C fiows tion of the winding in such direction includes the contact part 15 of electrode 11, the gap between the contact parts I 15 and 19,- and a longitudinal section of the reed 17. Energization of the Winding 23 by current flowing in the opposite direction from that shown produces magnetic flux which flows axially in the direction of the arrow F2 through a first path including a longitudinal part of the reed 17, the gap between contact parts 19 and 15, and a longitudinal part of the contact part 15, and through a second pathincluding a longitudinal part of the need 17 and a longitudinal part of the contact part 16. Operation of the switch in response to application of an external field will be described hereinafter.

' As described more fully in the previously mentioned application, the permanent magnet 20 develops magnetic fluxes which follow paths other than the path traversed by the flux A and which tend to adversely aifect operation of the switch particularly when the contact parts 15 and 19 are in engagement. A first one of these so-called adversefluxes follows a path which may be traced from the last of these adverse fluxes flows from the North pole of 'magnet 20 through a part of the electrode 11 back to the South pole of magnet 20 without traversing the con-.

tact parts 15 and 19. In order to minimize the magnitudes of these adverse fluxes and to neutralize their effects the space between the terminal parts 13 and 14 of the electrodes 11 and 12 adjacent the left hand end of the tube It is made comparatively large, and the spacing between the contact parts 15 and 16 adjacent the stepped areas thereof is made comparatively small. The space between the terminal parts 13 and 14 is at least twice the spacing be tween the contact parts 15 and 16, and preferably about three times such spacing. The first and second adverse fluxes above described flow in opposite directions between the contact parts 15 and 19 and the switch is so designed that these fluxes are equalized so that substantially zero resultant flux from the magnet20 traverses the contact parts 15 and 19.

The switch operating characteristics, contact holding forces and ,themagnitude of the external field required to transfer the reed are conveniently varied by varying the inductions of the magnets 20 and 22 and by varying the longitudinal position of the magnet 22relative to the switch contacts. The desired magnet inductions are obtained by first magnetizing the magnets 20 and 22 to saturation and then dem-agnetizing the magnets to the desired stable residual induction levels. The inductions of the magnets 20 and'22 can be independently set after the switch is assembled and before [the magnet 22 is permanently secured to the tube. Thereafter, the magnet 22 can be adjusted along the tube to establish the desired precise switch characteristics and can then be attached to the tube in the adjusted position. By properly selecting the inductions of the magnets 20 and 22 and by proper selection of the longitudinal position of the magnet 22 relative to the switch contacts various operating characteristics may be realized. For example, the inductions of the magnets and the position of the magnet 22 can be selected so that the reed 17 normally engages a selected one of the contact parts 15 and 16. In addition, the arrangement can be such that predetermined different ampere-turns of the coil 23 are required to release the reed 19 from the contact parts 15 and 16, or that substantially the same ampere-turns of the coil23 will result in switching of the reed in either direction.

To describe the operation, let it be assumed that the reed 17 is in engagement with the contact part 16. For

this assumption flux from magnet 20 traversing the path including closed contact par-ts 16 and 19 exceeds the flux from the magnet 22 traversing the path including the gap between the contact parts 15 and 19. The resulting net magnetic attraction provides an adequate force holding the reed 17 in engagement with the contact part 16. If now the winding 23 is energized by current flowing in the directions of the arrow C a magnetic flux is developed which flows axially in the direction of the arrow F1 and which traverses the contact parts 16 and 19 in opposition to the flux from magnet 20, and which traverses the contact parts 15 and 19 in the same direction as flux from the magnet 22. As the strength of this external field is increased, the magnetic attraction of the reed 19 to contact part 16 is reduced and the attraction of the reed 17 to contact part 15 is increased until the net force results in a transfer of the reed 17 from contact part 16 to C011? tact part 15 with a snap action.

With the reed 17 now engaging contact part 15, the

flux from magnet 22 traversing the path including closed contact parts 15 and 19 exceeds the flux from magnet 20 traversing the gap between contact parts 16 and 19 so that the reed 17 is held in engagement with contact part 15 even after removal of the external field which caused movement of the reed 17 to such position. If the winding 23 is now energized by current flowing in the directionopposite to that shown, magnetic flux is produced which flows axially in the direction of the arrow F2, this flux opposing flux from the magnet 22 in the path including the contact parts and 19, and reinforcing flux from the magnet in the path including the contact parts 16 and 19. When energization of the winding 23 attains a certain level, the reed will transfer with a snap action from the contact part 15 to the contact part 16 where the reed will remain after removal of the. external field.

Referring now to FIG. 2 there is illustrated a latch type reed switch S which differs from the switch S of FIG. 1. The switch S of FIG. 2 includes a pair of permanent magnets and 31 corresponding respectively to the permanent magnets 20 and 22 of the device of FIG. 1, and in the device of FIG.,2 both of the permanent magnets 30 and 3 1 are located externally of the tube 32. It is noted that by positioning the permanent magnet 30 externally of the tube, the tube may be of considerably smaller size than the corresponding tube 10 of the switch S of FIG. 1.

The switch S" includes a first fixed electrode 33 corresponding to the electrode 11 of the device of FIG. 1 and formed of electrically and magnetically conductive material. The electrode 33 is supported by the tube 32 at the upper left hand end thereof as viewed in FIG. 2. The electrode 33 is of one piece construction and includes a terminal part 34 outside the tube and a contact part 35 within the tube. A second fixed electrode 36 correspondling to electrode 12 of the device of FIG. 1 is supported by the tube 32 at the lower left hand end thereof beneath the electrode 33 as viewed in FIG. 2. The electrode 36 is formed of electrically and magnetically conductive material and is of two part construction. The electrode 36 includes a terminal part 37 outside the tube which is welded or otherwise fixed to the upper surface of the magnet 30, and includes also a contact part 38 having a portion 39 outside the tube which is secured to the upper surface of the magnet 30 to support the magnet 30. The contact parts 35 and 38 cooperate with a deflectable reed 46 supported by the tube at the right hand end thereof and having a contact part 41 extending between and overlapping the contact parts 35 and 33. The basic double throw feature of the switch S of FIG. 2 is disclosed and claimed in the aforementioned Werts application.

Operation of the switch S of FIG. 2 is the same as that of the switch S of FIG. 1. Suffice it to say that when an operating winding (not shown) is energized by current flowing in a direction to produce magnetic flux eflective to deflect the reed 49 out of engagement with contact 38 and into engagement with cont-act 35, the reed will remain in the deflected position after deenergization of the winding (not shown). If the winding (not shown) is energized in the opposite direction, the reed will then be deflected out of engagement with contact 35 and into engagement with contact 38, and will remain in this position after the winding (not shown) is deenergized. One advantage of locating the magnet 30 outside the tube 32 is that the diameter and length of the tube can be materially reduced as compared to such dimensions of the tube 10 in the embodiment of FIG. 1. Another advantage is that the magnet 30 can be secured in position after the tube 32 has been sealed thereby eliminating any possibility of damage to the magnet which might occur as a result of the high sealing temperature involved.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the-art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A switch comprising a sealed tube, a pair of electrically and magnetically conductive electrodes mounted by said tube having terminal parts outside the tube and having contact parts within the tube in spaced relation,

an electrically and magnetically conductive defiectable reed mounted in said tube and having a terminal part outside the tube, said reed extending longitudinally of the tube between and in overlapping relation with the contact parts of said electrodes for defiection'into and out of engagement with the contact parts inresponse to the application of an external magnetic field, a first permanent magnet positioned with its poles spaced longitudinally of said tube for attracting said reed towards the contact part of a first one of said electrodes, and a second permanent magnet spaced from the second electrode with its poles spaced longitudinally of said tube for attracting the reed towards the contact part of the'second electrode, said permanent magnets being poled in the same direction so that magnetic fluxes from the two magnets traverse a substantial longitudinal portion of the reed in opposing directions and the flux from each magnet traverses a portion of a separate one of said electrodes, each permanent magnet being effective to hold the reed in engagement with the contact part of the associated electrode subsequent to removal of an external magnetic field.

2. A switch as defined in claim 1 wherein the second permanent magnet is located outside the tube on the external surface thereof.

3. A switch as defined in claim 1 wherein said first permanent magnet is located outside said tube on said first electrode, said second permanent magnet being located outside the tube on the external surface thereof.

4. A switch comprising a sealed tube, a pair of electrically and magnetically conductive electrodes mounted by said tube having terminal parts outside the tube and having contact parts Within the tube in spaced relation, an electrically and magnetically conductive deflectable reed mounted in said tube and having a terminal part outside the tube, said reed extending longitudinally of the tube between and in Overlapping relation with the contact parts of said electrodes for deflection into and out of engagement with the contact parts in response to the application of an external magnetic field, a first permanent magnet on a first one of said electrodes spaced longitudinally from said reed for attracting said reed toward the contact part of said first electrode, a second permanent magnet located outside the tube on an external surface thereof for attracting said reed toward the contact part of the second electrode, said permanent magnets having poles spaced longitudinally of the tube and being poled in the same direction so that magnetic fluxes from the two magnets traverse a substantial longitudinal portion of the reed in opposing directions and the flux from each magnet traverses a separate one of said electrodes, each permanent magnet being effective to hold the reed in engagement with the contact part of the associated electirode subsequent to removal of an external magnetic eld.

5. A switch as defined in claim 4 wherein said first permanent magnet is located outside said tube.

6. A switch comprising a sealed tube, a first electrically and'magnetically conductive electrode of integral construction mounted by said tube and having a terminal part outside said tube and a contact part within the tube, a second electrically and magnetically conductive electrode of two-part construction including separate terminal and contact parts with the terminal part having portions both inside and outside of said tube and with the contact part within said tube, a first permanent magnet mounted on the portion of the terminal part of said second electrode which is inside said tube and connected to and mounting the contact part of said second electrode, an electrically and magnetically conductive defiectable reed mounted by said tube and having a terminal part outside said tube, said reed extending longitudinally of said tube between and in overlapping relation with the contact parts of said electrodes for deflection into and out of engagement with said contact parts in response to the application of an external magnetic field, said first magnet being spaced 7 longitudinally from said reed with its poles spaced longitudinally of said tube for attracting said reed toward the contact part of said second electrode, said reed when deflected into engagement with the contact part of either of said electrodes developing a spring force which urges the reedlaway from the engaged contact part toward the other contact part, the relative positions of said first magnet, said reed and said electrodes being selected such that magnetic flux from the first magnet traverses the first magnet and the reed in series in thesame direction substantially longitudinally of the tube, and such that substantially zero resultant magnetic flux from the first magnet passes between the reed and the contact part of the first eletcrode, and a second permanent magnet positioned outside said tube on the external surface thereof for attracting said reed toward the contact part of said first electrode, said second magnet having poles spaced longitudinally of the tube and being poled in the same direction as said first magnet suchthat magnetic fluxes produced by the two magnets traverse a substantiallongitur &

dinal portion of the reed in opposing directions, each permanent magnet being effective to hold the reed in engagement with the contact part of the associated electrode subsequent to removal of anexternal magnetic field.

References Cited by the Examiner UNITED, STATES PATENTS 2,898,422 8/59 Peek 200-93 2,907,846 10/59 Wilhelm 200--93 2,957,961 10/60 Juptner 200-87 3,008,020 11/61 Mason 200-83 3,048,677 8/62 Hellstrom et a1. 200-87 3,061,696 10/62 Peek 20093 3,117,202 1/64 Werts a- 200-87 3,125,650 3/64 Ellwood 200-87 BERNARD A. GILHEANY, Primary Examiner.

20 ROBERT K. SCHAEFER, Examiner. 

1. A SWITCH COMPRISING A SEALED TUBE, A PAIR OF ELECTRICALLY AND MAGNETICALLY CONDUCTIVE ELECTRODES MOUNTED BY SAID TUBE HAVING TERMINAL PARTS OUTSIDE THE TUBE AND HAVING CONTACT PARTS WITHIN THE TUBE IN SPACED RELATION, AN ELECTRICALLY AND MAGNETICALLY CONDUCTIVE DEFLECTABLE REED MOUNTED IN SAID TUBE AND HAVING A TERMINAL PART OUTSIDE THE TUBE, SAID REED EXTENDING LONGITUDINALLY OF THE TUBE BETWEEN AND IN OVERLAPPING RELATION WITH THE CONTACT PARTS OF SAID ELECTRODES FOR DEFLECTION INTO AND OUT OF ENGAGEMENT WITH THE CONTACT PARTS IN RESPONSE TO THE APPLICATION OF AN EXTERNAL MAGNETIC FIELD, A FIRST PERMANENT MAGNET POSITIONED WITH ITS POLES SPACED LONGITUDINALLY OF SAID TUBE FOR ATTRACTING SAID REED TOWARDS THE CONTACT PART OF A FIRST ONE OF SAID ELECTRODES, AND A SECOND PERMANENT MAGNET SPACED FROM THE SECOND ELECTRODE WITH ITS POLES SPACED LONGITUDINALLY OF SAID TUBE FOR ATTRACTING THE REED TOWARDS THE CONTACT PART OF THE SECOND ELECTRODE, SAID PERMANENT MAGNETS BEING POLED IN THE SAME DIRECTION SO THAT MAGNETIC FLUXES FROM THE TWO MAGNETS TRAVERSE A SUBSTANTIAL LONGITUDINAL PORTION OF THE REED IN OPPOSING DIRECTIONS AND THE FLUX FROM EACH MAGNET TRAVERSES A PORTION OF A SEPARATE ONE OF SAID ELECTRODES, EACH PERMANENT MAGNET BEING EFFECTIVE TO HOLD THE REED IN ENGAGEMENT WITH THE CONTACT PART OF THE ASSOCIATED ELECTRODE SUBSEQUENT TO REMOVAL OF AN EXTERNAL MAGNETIC FIELD. 